1. Field of the Invention
This invention relates to a color liquid crystal display device, more particularly to a color liquid crystal display device having high brightness and high contrast.
2. Description of the Related Art
Recently, liquid crystal display devices have been increasingly developed due to their characteristics, such as light weight, thin profile, and power saving.
It is desirable to provide a liquid crystal display device having high brightness and high contrast.
JP 10-148712 discloses a color resist composition for a color filter of a liquid crystal display device. An anthraquinone-based red pigment such as C.I. Pigment Red 177 is used in a red pixel of the color filter. The red pigment is mechanically micronized to improve the dispersion thereof, such that the contrast of a liquid crystal display device can be increased thereby. However, the brightness of the color filter can not be effectively enhanced due to the spectral properties of the red pigment. Moreover, in JP 10-148712, an azo-based red pigment such as C.I. Pigment Red 166 is mixed with C.I. Pigment Red 177 and yellow pigments so as to improve color characteristics. Although the color reproduction area of the color filter is expanded, the contrast can not be enhanced.
In JP 11-231516 and JP 2002-328217, C.I. Pigment Red 254, a diketo-pyrrolopyrrole-based red pigment, is used. Compared to C.I. Pigment red 177, the transmission spectrum at about 600 nm of C.I. Pigment Red 254 shifts toward shorter wavelength, and the red absorption of the backlight is reduced so as to enhance the brightness. However, the cohesion among the micronized particles of C.I. Pigment Red 254 is too strong. Therefore, it is difficult to disperse the micronized particles of C.I. Pigment Red 254, such that the contrast can not be enhanced.
Therefore, it is still required in the art to provide a color liquid crystal display device having both high brightness and high contrast.